Air atomizing oil burner



Oct. 28, 1969 E. G. BARRY AIR on/ 12186 011; BURNER Filed Aug '28. 1967INVENTOR. Edward 6. Barry United States Patent 3,474,969 AIR ATOMIZINGOIL BURNER Edward G. Barry, Woodbury, N.J., assignor to Mobil OilCorporation, a corporation of New York Filed Aug. 28, 1967, Ser. No.663,807 Int. Cl. F23d 11/04; B05b 7/28 US. Cl. 239400 6 Claims ABSTRACTOF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the inventionThis invention relates to an improved oil burner. More particularly, itrelates to an improved air atomizing oil burner.

Description of the prior art A problem in the oil burner art has been toprovide a low cost air atomizing oil burner that is capable of eflicientand reliable operation at low capacities on a distillate fuel. Researchhas been directed to providing such a burner for use in residentialheating systems, space heaters, portable heaters, water heaters,incinerators and the like. Since the oil burner may be used inresidential equipment, it must maximize combustion to provide clean,odor-free burning.

To aid in the development of low capacity air atomizing oil burners, theAmerican Petroleum Institute published A Survey of Components for UseWith Air- Atomizing Oil-Burner Nozzles, API Publication 1720, October1961, by M. L. Yeager and C. L. Cofiin. This survey discusses well knownsystems which use a low pressure nozzle, and systems which use a siphontype nozzle. In the systems using a low pressure nozzle, oil is pumpedto the nozzle under a slight pressure, for example 1 to p.s.i. and lowpressure air is supplied to the nozzle to atomize the oil. In thesystems comprising a siphon type nozzle, the flow of low pressure airthrough the nozzle provides both suction to lift the oil from areservoir and energy to atomize the oil. A siphon type system that wasconsidered by the authors of the survey is described in Air-AspiratedOil Burners, Conference Paper CP 61-11 by B. R. Walsh, Proceedings: APIResearch Conference on Distillate Fuel Combustion, API Publication No.1541, Mar. 14-15, 1961.

The foregoing publications are concerned with providing primary air to alow capacity air atomizing nozzle to atomize the fuel supplied to thenozzle, and, in a siphon type system, to also provide suction to liftthe fuel oil. The publications do not contemplate the need for supplyingsecondary air for combustion of the atomized fuel. It is known to use afan to supply secondary air. However, a fan adds to the expense, issubject to breakdowns, and raises control difficulties when theoperating conditions of the burner are varied.

SUMMARY OF THE INVENTION In accordance with the present invention, thereis provided an air atomizing burner which comprises a chamber having anend thereof opened to a combustion environment such as a furnace. An airatomizing nozzle is mounted interiorly of the chamber in the vicinity ofthe opened end. Means are provided for supplying fuel oil to the nozzle.A pressurized air reservoir means is operatively connected to the nozzleand the chamber by conduit means to provide a source of pressurizedprimary air to the nozzle and a source of pressurized secondary air tothe chamber. The primary air source is used to atomize the fuel suppliedto the nozzle, and the secondary air is used to aid in combustion of theatomized fuel. Means are also provided to supply pressurized air to thereservoir means. Thus, the present invention advances the art byutilizing as secondary air the air not necessary for primary air. Bycontrolling the means for providing the pressurized air to the reservoirmeans, sufiicient primary and secondary air may be provided to operatethe system.

In accordance with another aspect of the invention there is provided anair compressor for supplying compressed air to the reservoir means. Theair compressor has a round bore housing and a rotor eccentricallymounted in relation to the longitudinal axis of the bore housing. Aplurality of vanes are rotatable about the axis of the housing. As therotor rotates the vanes are driven by the rotor to provide relativemotion between the vanes and the rotor.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a schematic diagram of anair atomizing burner with a sectional view of its blast tube,

FIGURE 2 is a schematic sectional view of an air compressor, and

FIGURE 3 is a cross-sectional view of the burner along line IIIIII ofFIGURE 1 therefor.

DESCRIPTION OF SPECIFIC EMBODIMENTS Referring to FIGURE 1, the aircompressor 10 is shown having an intake port 11 opened to the atmosphereand an exhaust port 12 connected to a conduit 13. The air compressor 10may be of the type shown in FIGURE 2 wherein three vanes 16 pivot in thecenter 17 of a round bore housing 18. The vanes 16 are driven by aneccentrically mounted rotor 19 which rotates on its own center 20. Thevanes 16 are radial to the housing 18 to provide a sealing effect.However, a few thousandths of an inch clearance is provided at the vanetips to minimize frictional loss. The displacement of the pump is afunction of its vane-to-rotor center distance and the rotor diameter andlength. The rotor 19 is generally cylindrical in shape and has threeslots formed in its outer surface to permit relative movement betweenthe vanes 16 and the rotor 19.

The compressor shown in FIGURE 2 is described in greater detail in thepapers by W. B. Thompson that were published in the General MotorsEngineering Journal, Third Quarter 1966, pp. 30-35, and in The GeneralMotors Air Injection Reactor Air Pump, Automotive Engineering Congress,Detroit, Mich., Jan. 10-14, 1966, SAE 660108. A compressor of the typeshown in FIGURE 2 mav be Chevrolet part No. 5696211 C'FB3.

The rotor of the air compressor 10 is driven by an electric motor 14 sothat a flow of compressed air is supplied to a plenum chamber 15 via theconduit 13. A primary air conduit 21 connects the plenum chamber 15 to asiphon type air atomizing nozzle 30, and a secondary air conduit 31connects the plenum chamber 15 to a cylindrically shaped secondary airhandling tube or blast tube 32 that has one end 33 thereof opened to acombustion environment, such as a furnace. The secondary air handlingtube 32 provides the air necessary for combustion of the atomized fuelexhausting from the nozzle 30. The primary air conduit 21 extendscentrally of the secondary air handling tube 32 and the nozzle 30 islocated in the vicinity of the opened end 33 of the secondary airhandling tube 32.

A pressure control valve 134 is positioned in the secondary air conduit31 to control the pressure within the plenum chamber 15. Thus, theplenum chamber acts as a primary air reservoir and all air not necessaryfor the nozzle passes through the secondary air conduit 31 to thesecondary air handling tube 32. A relief valve 135 vented to theatmosphere may be provided in the secondary air conduit 31 downstreamfrom the pressure control valve 134 to prevent the secondary airpressure from exceeding a predetermined maximum.

As discussed above under the Description of the Prior Art, siphon typeair atomizing nozzles are known in the art. Siphon type nozzles suitablefor the practice of this invention are manufactured by DelavanManufacturing Company, West Des Moines, Iowa and are listed in DelavansCatalog 600 under Catalog Nos. SNA .20, SNA .30, SNA .40, SNA .50, SNA.65, SNA .75, SNA .85 and SNA 1.00. Capacities of representative Delavannozzles are shown in the following table.

3 p.s.i. Air 4 p.s.i. Air 5 p.s.i. Air Lift Height Catalog Fuel, Air,Fuel, Air, Fuel, Air, Number g.p.h. c.f.m. g.p.h. c.f.m. g.p.h. c.f.m.(inches) .19 .36 .23 .45 .25 .49 1 SNA .20 .16 .36 .20 .45 .22 .49 4 .14.36 .17 .45 .20 .49 7 .48 .50 .54 .50 .58 .65 1 SNA .50 43 50 .50 .59 53G5 4 .38 .50 .46 .50 .48 .65 7 96 73 1. 10 91 1. 1. 02 1 SNA 1.00 84 .731.00 .91 1. 06 1. 02 4 72 .73 .90 .91 .97 1.02 7

The capacities shown in the above table are based on the minimum airpressures and air volumes possible for good atomization and liftcharacteristics.

The primary air flow from the primary air conduit 21 through the siphontype nozzle provides suction to lift the oil from an oil reservoir or aconstant level d vice through an oil conduit 34 to the nozzle 30, andenergy for atomizing the oil. The oil conduit 34 bends within the nozzle30 to carry the oil along the longitudinal axis of the nozzle 30 to thevicinity of the nozzle orifice. In the nozzle 30, the compressed primaryair passes exteriorly of the portion of the oil conduit 34 within thenozzle 30 and is directed inwardly and in the direction of flow throughgrooves formed in a swirl stern that is mounted axially of the outletend of the oil conduit 34. The primary air flow causes the oil to beaspirated from the outlet end of the oil conduit 34 and through an axialinlet in the swirl stem, and to be atomized by the primary air in anozzle swirl chamber prior to discharging through the nozzle orifice.

Referring to the above table, the lift height noted in the table is thedistance L between the longitudinal axis of the nozzle 30 and the levelof the oil in the reservoir 35. As shown in the table, a SNA .20 nozzlereceiving primary air at 3 PS1. is capable of lifting .19 g.p.h. of fuela lift height of 1 inch and of supplying .36 c.f.m. of primary air foratomization. In comparison, a SNA 1.00 nozzle receiving primary air at 5p.s.i. is capable of lifting .97 g.p.h. of fuel a lift height of 7inches and of supplying 1.02 c.f.m. of primary air for atomization. Ifthe combustion application does not permit a constant level device 35, afuel metering pump may be used to provide the necessary flow rate offuel oil.

Therefore, the pressure control valve 134 is set to maintain thepressure of the primary air in the plenum 15 at a value sufiicient tomeet the desired characteristics of the nozzle 30. For example, when anyone of the Delavan nozzles listed in Catalog 600 is used, the pressurecontrol valve 134 preferably should be capable of controlling thepressure within the plenum 15 between about 2 p.s.i. and 5 p.s.i.

An air difiuser may be mounted traversely of the longitudinal axis ofthe secondary air handling tube 32 to evenly distribute and impart arotary motion to the secondary air passing through the handling tube 32.The diffuser 40 shown in cross section in FIGURE 1 and in FIGURE 3 hastwo series 45, 46 of slots which impart a rotary motion to the secondaryair. Any well known diffusers may also be used, for example a radiallymounted fin arrangement.

When the compressor described hereinabove with reference to FIGURE 2 isused, the electric motor 14 is preferably operated at 1725 r.p.m. If anincreased air compressor output is required, a gear arrangement may beused to increase the speed of the rotor.

Another means of increasing the amount of secondary air for combustionmay be provided by mounting a fan (not shown) to the left of FIGURE 1and within a structure containing the combinations of elements discussedhereinabove. The structure would require sufficient air ports and permitthe passage of air from the fan to the combustion environment via meansexterior to the secondary air handling tube 32.

An electrode assembly 50-52 is provided to ignite the combustiblemixture of oil and air in the vicinity of the nozzle orifice. Any numberof well known electrode assemblies may be used, and they usuallycomprise a high voltage transformer 51 for supplying a high voltage toan electrode 50 via a pair of leads 52.

Suitable safety devices are contemplated. For example, a cadmium sulfidephotoelectric cell 53 may be mounted to sense the flame. If thephotoelectric cell fails to sense the flame, it actuates a switchingdevice (not shown) connected to the cell leads 54 to remove electricalpower from the transformer 51, from the motor 14 and other electricallyoperated devices that may be used.

A stack switch may also be used to remove electrical power fromelectrically operated elements in a burner when the heat changeindicates that combustion has ceased.

The invention also contemplates the use of well known low pressurenozzles wherein the fuel oil is pumped to the nozzle under low pressure,for example 1 to 15 p.s.i.

Since various changes and adaptations may be made to the disclosedspecific embodiments without departing from the intent of the invention,it is intended that the foregoing description be considered asillustrative of the present invention and that the only limitations arethose recited in the appended claims.

What is claimed is:

1. An air atomizing burner comprising a blast tube having an opened endthereof adapted to be positioned in a combustion environment, an airatomizing nozzle mounted interiorly of said blast tube for directingatomized fuel oil through said opened end, means for supplying fuel oilto said nozzle, means for providing a reservoir of pressurized air,first conduit means operatively interconnecting said reservoir means andsaid nozzle for providing a source of pressurized primary air to saidnozzle to atomize the fuel supplied to said nozzle, second conduit meansoperatively interconnecting said reservoir means and said blast tube forproviding a source of pressuized secondary air to said blast tube, meansin said second conduit means for maintaining the air in said reservoirmeans at a predetermined pressure, and means for supplying compressedair to said reservoir means.

2. An air atomizing burner comprising a chamber having an end thereofopened to a combustion environment, an air atomizing nozzle mountedinteriorly of said chamber in the vicinity of said opened end, means forsupplying fuel oil to said nozzle, means for providing a reservoir ofpressurized air, first conduit means operatively interconnecting saidreservoir means and said nozzle for providing a source of pressurizedprimary air to said nozzle to atomize the fuel supplied to said nozzle,second conduit means operatively interconnecting said reservoir meansand said chamber for providing a source of pressurized secondary air tosaid chamber, means in said sec- 0nd conduit means for maintaining theair in said reservoir means at a predetermined pressure, means in saidsecond conduit means and downstream of said pressure maintaining meansfor preventing the secondary air provided to said chamber from exceedinga predetermined pressure, and means for supplying compressed air to saidreservoir means.

3. The burner of claim 1 including means for distributing the secondaryair throughout said blast tube and for imparting rotary motion to thesecondary air.

4. The burner of claim 1 wherein said nozzle is a siphon type nozzle.

5. The burner of claim 4 wherein said means for supplying compressed airto said reservoir means comprises an air compressor having a round borehousing, a rotor eccentrically inounted in relation to the longitudinalaxis of the housing, a plurality of vanes rotatable about the axis ofthe housing, and extending through said rotor,

and means for driving said rotor, whereby the vanes are driven by therotor to provide relative movement between the vanes and the rotor.

6. The burner of claim 1 further including means in said second conduitmeans and downstream of said pressure maintaining means for preventingthe secondary air provided to said blast tube from exceeding apredetermined pressure.

References Cited UNITED STATES PATENTS 3,344,834 10/1967 Feinman et a1.23940O EDWARD G. FAVORS, Primary Examiner US. Cl. X.R.

